Disclosed herein is an apparatus and method that controls feed commitments based on feedable capacity.
Presently, a media sheet marking device, such as a copier or printer, that feeds media sheets can include a scheduler and a media sheet source, as well as a marking engine and a media sheet stacker. In a marking engine, such as a xerographic marking engine, a photoconductive insulating member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within a document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a developing material. Generally, the developing material comprises toner particles adhering triboelectrically to carrier granules. The developed image is subsequently transferred to a sheet of media, such as a sheet of paper, a transparency, or other sheet of media, that is fed from a media sheet source. A stacker can then stack the marked media sheets. A scheduler can schedule feed commitments for a number of sheets to be fed by the media sheet source, marked by the marking engine, and stacked by the stacker. For example, the scheduler can inform each element that a certain number of sheets will be processed by the elements. As one of the scheduled elements, a media sheet source must plan and commit to a variable number of feed commitments.
Unfortunately, the feedable capacity of the media sheet source may not be sufficient to satisfy outstanding feed commitments scheduled by the scheduler. For example, the media sheet source feed tray may not contain enough media sheets to meet the outstanding feed commitments. An unscheduled shutdown or jam can result from the media sheet source attempting to feed sheets after the feed tray is empty, which can require a machine operator to clear the entire media sheet path. Attempting to feed sheets after the feed tray is empty can also result in damage the media sheet source. Furthermore, other elements, such as the marking engine and the stacker can be damaged if they attempt to process scheduled, but unfed sheets. This can occur when a media sheet source does not include a sheet sensor for sensing the availability of sheets. To attempt to avoid damage, a media sheet source may stop feeding sheets prematurely. However, because the media sheet source cannot adequately control its feed commitments based on its feedable capacity, it will stop feeding sheets even though the feed tray it not empty.
Thus, there is a need for method and apparatus that controls feed commitments based on feedable capacity.